L-lysine, one of essential amino acids, is widely used as animal feed, medicament, food, etc. A demand thereon has been recently increased according to a tendency to prevent environmental pollution by livestock wastewater through reinforcing a regulation on nitrogenous or phosphorous ingredients in livestock excretions. It is estimated that L-lysine as an additive to animal feed had a market scale of about five hundred thousands tons in 1999, and expected that a demand thereon will continuously rise by about an average of 10% every year. As described above, L-lysine is a large item in the fermentation product market. Therefore, it is expected that a big economic effect will be obtained by improving L-lysine productivity through development of a new L-lysine-producing strain or improving its fermentation process.
L-lysine has been heretofore produced using various auxotrophic strains, or drug-resistant or sensitive strains belonging to Coryneform bacteria. It has also been produced using an antibiotic-resistant strain, for example, bacitracin-resistant (Japanese Patent No. 1,765,413), sulfa drug-resistant (Korean Patent Laid-Open No. 81-1746) or iturin-resistant (Japanese Patent No. 2,578,413) strain, or a strain with resistance to two or more antibiotics, such as streptomycin and rifampicin (U.S. Pat. No. 4,623,623). However, a strain with resistance to an antibiotic, monensin, has never been reported.